My car (2007 Mustang v6 - 156k miles) didn’t pass inspection due to a check engine light on. Long story short, catalytic converter needed replacement. However, after getting my car back from the mechanic, I noticed the car’s engine sounding rougher than before when driving it home about 30 minutes from the shop. The next day, I planned to take it to state inspection but I stopped by the store first. Then I couldn’t start anymore. It tried to crank up but it wouldn’t start. Black smoke was blowing out of the exhaust and it smelled fuel all over.
I had it towed to the shop and I was told it was the spark plug and the crank sensors. Had those replaced and car still does not work. Now they’re telling me it’s the pistons and the motor needs lots of work. I’m starting to doubt the shop I brought it to. They did a full diagnostic before changing the catalytic converter and they told me the motor is fine but I needed new brakes and differential gasket. But that was it.
I would appreciate any opinions on what I should do next. SHould I rebuild engine? Changed shop? Did they do anything to the catalytic converter that cause engine shutdown?